The chord A7 that is shown here contains the notes: A, E, G, C#. The root of the chord is A. The scale from which the chord is derived is Dominant seventh chord (1–3–5–♭7), and the degrees of the scale are: 1, 3, 5, ♭7.
To play the chord A7 shown above, place your fingers as follows:
On string number 5, on fret number 0 (open string)
On string number 4, on fret number 2 with finger number 1 (index finger)
On string number 3, on fret number 0 (open string)
On string number 2, on fret number 2 with finger number 3 (ring finger)
On string number 1 (the thinnest), on fret number 0 (open string)
Start strumming from string number 5 (notice not to play string 6).